The present invention is related to flat laminate parts consisting of a substrate and a cover layer with an auxiliary pull-off means for said cover layer or parts thereof.
It is often necessary to protect one or both surfaces of a flat substrate or one or both open surfaces of a flat laminate, by a cover layer before the final use thereof. Such a cover layer is necessary for instance due to the adhesive properties of said surface or its sensitivity to mechanical damage or in order to avoid evaporation of highly volatile components from a layer by way of such a surface. The cover layer in general is kept to the substrate layer by adhesive additions to said substrate layer or by the self-adhesive properties of the surface of the substrate layer which adhesive forces may be overcome by the application of mechanical pull-off forces. The problem with such compositions is to make the combination of the substrate layer and the cover layer such that both layers are securely held together but the pull-off of the cover layer or of parts thereof is easy and readily possible.
There are known already several propositions to solve this problem. Thus, a mere tearing of the laminate allows to use the finger nail to grasp a part of the cover layer and pull it off from the substrate layer and by using this part of the cover layer as grasp part to thereby allow a complete pull-off of the cover layer. It is furthermore known to compose the cover layer of several parts with a total surface larger than the surface of the substrate layer thereby producing overlapping parts in the surface of the cover layer which overlapping parts are used as grasp parts and auxiliary pull-off means in the cover layer. If no such overlapping parts are provided in the cover layer, grasp parts in the cover layer are known to be produced by sharply bending the laminate at one or several of its edges thereby causing the cover layer to be solved from the substrate layer at such edges if the cover layer is rigid enough to produce sufficient peel-off forces by such rigidity. Another known possibility to produce grasp parts for the cover layer is to cover the substrate layer by a cover layer larger than the substrate layer. Furthermore, another known means to ease the pull-off of the cover layer from the substrate layer is to produce linear cuts or preset linear breaking lines in the cover layer allowing to produce lines in the cover layer by pulling and bending the laminate wherefrom the pull-off of the cover layer may be started. Still furthermore, it is known to incorporate into the laminate a wire or a strap between the cover layer and the substrate layer said wire or strap projecting over the edges of the laminate which wire or strap serves as an auxiliary pull-off means for the cover layer from the substrate layer. It is furthermore known a flat laminate part consisting of a substrate layer and a cover layer the adhesive forces between said substrate layer and said cover layer being such that both layers are securely held together, but a pull-off of said cover layer is readily possible by hand or mechanically, said flat laminate part having additionally an auxiliary pull-off means to so pull-off said cover layer or parts of said cover layer by hand or mechanically said auxiliary pull-off means comprising preset cuts or breaking lines in the cover layer, wherein said preset cuts or preset breaking lines in said cover layer are positioned and formed such that there is at least one part of the cover layer which can be grasped per each part of said cover layer to be pulled off, said grasp part getting exposed by bending the flat laminate part to form a concave curvature of the surface of said cover layer opposite to the surface of said cover layer adhearing to said substrate layer, the at least two points of attack of the force producing such bending of the flat laminate part being distributed over the surface of the flat laminate part such that the forces acting substantially vertically from the laminate in the bend, result in a peeling off of said grasp part of said cover layer.
All these proposals to solve the problem are not satisfactory because they either necessitate additional material or complicated procedures to produce them or only give a sufficient large grasp part to easily pull-off the cover layer from the adhearing substrate layer if there is a sufficient difference in the stiffness of the cover layer and of the substrate layer.